The present invention relates to multi-unit railroad freight cars, and in particular to such a car including container well units.
Within the limits of available space along railroad tracks and the ability of the tracks to support loaded freight cars safely, it is economically desirable to carry as heavy a load of revenue-earning cargo as possible in a given train length. Increased cargo weight for a given train length gives increased cost efficiency, since the train crew wages, train mile and fuel expenses, and locomotive costs are shared by the increased amount of cargo revenue.
Freight cars including multiple well units for carrying stacked intermodal cargo containers are well known. Some of these cars use shared trucks to support adjacent well units. Others use drawbars to interconnect adjacent units that are each fully supported by their own trucks. In both of these types of multi-unit container well cars the large space between the ends of containers carried in adjacent well units results in a significant amount of aerodynamic drag during train operation and leaves a significant portion of the length of a train in which no cargo containers are present.
Within the railroad industry there are regulations in effect limiting the maximum weight of a loaded intermodal cargo container, and railroad cars are designed with ample strength to carry various combinations of such cargo containers safely. For example, containers of nominal 20-foot length are limited to 52,900 pounds, nominal 40-foot containers are limited to 67,200 pounds and nominal 53-foot containers may be designed for either 56,700 pounds or 67,200 pounds. These maximum weights must be considered when loading a railroad car, in order not to overstress the car body or overload its trucks and thus concentrate too much weight on the tracks. As a result, a well unit carrying two fully loaded 20-foot containers may not be able to carry a fully loaded 40-foot or longer container safely in an upper tier.
While cargo capacity of such cars could be increased by building stronger container well bodies and using trucks of greater capacity, such bodies are so large and heavy that they have not been desired.
Utilization of shared trucks to support adjacent well units for carrying stacked containers in such multi-unit railroad freight cars can reduce the portion of the length of car in which there are no containers, but it also requires restricting the weight or number of containers which can be carried stacked in each of those adjacent well units carried by a single shared truck, in order to avoid overloading the shared truck. This often results in the unshared truck at each end of such a multi-unit well car being significantly under-loaded. As a result, such multi-unit well cars with shared trucks are often loaded to less than the optimum ratio of load weight to the length of a train of such cars.
What is desired, then, is a container-carrying multi-unit railroad freight car that has improved aerodynamic characteristics when loaded, that can be loaded to utilize more fully the available carrying capacity of the trucks with which such a multi-unit car is equipped, and in which the cargo weight for such a multi-unit car of a given length and container well size is maximized.
The present invention overcomes some of the aforementioned drawbacks and provides an answer to some of the shortcomings of the prior art railroad cars mentioned above by providing a multi-unit railroad freight car for carrying containers, in which at least two coupled container well units each include a container well and have respective body end structures, and in which a container-supporting bridge unit is located between the two container well units and has a pair of opposite ends each supported on the body of a respective one of the two adjacent container well units.
In one preferred embodiment of such a freight car a container support structure included in the bridge unit extends above the body bolster structure of the end of the adjacent container well unit.
In one embodiment of the invention the multi-unit freight car has a container-supporting bridge unit that includes an elongate center sill including opposite sill ends and has a center bearing associated with each of the opposite sill ends.
One aspect of the invention is the provision of a multi-unit railroad freight car that includes a bridge unit having a pair of transverse bolsters each attached to a center sill, and in which at least one of the transverse bolsters has a side bearing support leg aligned with a corresponding side bearing located on the body of an adjacent container well unit.
As one aspect of the invention a container-supporting bridge unit for a multi-unit railroad freight car includes a pair of opposite ends and a pair of container support arms associated with each of its opposite ends, and each of the opposite ends is supported by body end structure, such as a body bolster, of the adjacent container well unit of a multi-unit car including such a bridge unit.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.